/Engine/Source/Editor/GraphEditor/Public/SGraphNodeKnot.h
Handle clicking on the pin
virtual [FReply](API\Runtime\SlateCore\Input\FReply) OnPinMouseDown ( const [FGeometry](API\Runtime\SlateCore\Layout\FGeometry) & SenderGeometry, const [FPointerEvent](API\Runtime\SlateCore\Input\FPointerEvent) & MouseEvent )